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    Re: Alternate methods of sight reduction
    From: Zvi Doron
    Date: 2005 Dec 7, 10:04 +0000
    Hi Nels
     
    I have read the book you mentioned - the use of the standard slide rule it proposes does not come anywhere near the simplicity, elegance and accuracy of the Bygrave. The Bygrave however only deals with altitude and azimuth calculations for astronomical sight reductions - the Podmore book covers much more in other areas of navigation so is certainly useful in general.
     
    Kind regards
     
    Zvi

    Nels Tomlinson <nels.tomlinson@GMAIL.COM> wrote:
    Jim, you mentioned slide rules. I don't know about the Bygrave, but
    there is a book available on the web, called ``Slide Rule for Sea and
    Air Navigation'', by J. C. Podmore, available for download at
    http://sliderule.ozmanor.com/man/man-download.html (scroll about 4/5
    of the way down the page).

    Chapter VI - Dead Reckoning and Astronomical Calculations, mentions
    traverse tables, amplitudes, azimuth,prime vertical observations,
    errors, dip, parallax, refraction and ex meridians.

    That might help you get started using a regular sliderule for some of
    this stuff. The next chapter is on coastal navigation

    Nels

    On 12/6/05, Jim Hickey wrote:
    >
    >
    > Alternate methods of sight reduction
    >
    > First, allow me to introduce myself as a new member. My name is Jim Hickey.
    > My wife Judy and I currently live aboard our sailboat in St. Augustine,
    > Florida. I have been interested in celestial navigation for many years much
    > to the amusement and entertainment of my wife! Even got the programming bug
    > early on but have it under reasonable control at this time. It has been a
    > delight to read many of the fascinating postings for some time now.
    >
    > I have! a volume of Bowditch that discusses a variety of sight reduction
    > methods. I believe all the old table methods and more have been discussed.
    > Has anyone had access to or knowledge of the old slide rule type method that
    > is referenced? I believe the instrument was called a Bygrave computer which
    > looked cylindrical.
    >
    > As well, there is also a picture of a wonderfully elegant looking globe like
    > device that is set up with sliding arms that solves the navigational
    > triangle directly.
    >
    > I have been intrigued by these items for years and of course would love to
    > mess with them if I had the chance as I am sure many here would.
    >
    > Very curious to know how effective these approaches were and if there are
    > others etc. etc.
    >
    > Cheers,
    >
    > Jim

       
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